openGauss每日一练第15天 | openGauss逻辑结构：表管理 3

学习目标

学习查看表的相关信息

课程学习

1.测试环境准备

--首先创建一张测试表。
root@modb:~# su - omm 
omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

omm=# drop table if exists test;
NOTICE:  table "test" does not exist, skipping
DROP TABLE
omm=# create table test(
omm(# id bigint,
omm(# omm(# age  int default 20,
name varchar(50) not null,
omm(# primary key(id)
omm(#      );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "test_pkey" for table "test"
CREATE TABLE

2.在gsql中查看表的定义、模式和所有者

--在gsql中，使用\d tableNmae命令查看表的定义。
omm=# \d+ test;
                                 Table "public.test"
 Column |         Type          | Modifiers  | Storage  | Stats target | Description 
--------+-----------------------+------------+----------+--------------+-------------
 id     | bigint                | not null   | plain    |              | 
 name   | character varying(50) | not null   | extended |              | 
 age    | integer               | default 20 | plain    |              | 
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no
--在gsql中，使用\d tableNmae命令查看表的模式和所有者。
omm=# \dt+ test;
                                    List of relations
 Schema | Name | Type  | Owner |  Size   |             Storage              | Description 
--------+------+-------+-------+---------+----------------------------------+-------------
 public | test | table | omm   | 0 bytes | {orientation=row,compression=no} | 
(1 row)

3.查看某个模式下有哪些表

--查看public模式下的所有表名：
omm=# select table_name from information_schema.tables where table_schema='public';
 table_name 
------------
 test
(1 row)

4.查看一个表下有哪些约束

--查看约束名称、约束类型
omm=# select conname, connamespace, contype, conkey     
omm-#   from pg_constraint 
omm-#  where conrelid in (  select oid
omm(#                   from pg_class
omm(#                  where relname='test');
  conname  | connamespace | contype | conkey 
-----------+--------------+---------+--------
 test_pkey |         2200 | p       | {1}
(1 row)
--或者使用gsql的元命令\d tableName很方便地查看一个表上有哪些约束
omm=# \d test
             Table "public.test"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "test_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

1. 查看一个表属于数据库的哪个模式

--行转列omm=# \x
Expanded display is on.
omm=# select * from information_schema.tables where table_name = 'test';
-[ RECORD 1 ]----------------+-----------
table_catalog                | omm
table_schema                 | public
table_name                   | test
table_type                   | BASE TABLE
self_referencing_column_name | 
reference_generation         | 
user_defined_type_catalog    | 
user_defined_type_schema     | 
user_defined_type_name       | 
is_insertable_into           | YES
is_typed                     | NO
commit_action                | 

课程作业

1.创建表和约束

omm=# create table xx1(
omm(# id bigint,
omm(# name varchar(50) not null,
omm(# age  int default 20,
omm(# primary key(id)
omm(#      );
NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index "xx1_pkey" for table "xx1"
CREATE TABLE

2.使用\d tableNmae命令查看表的定义、模式和所有者

omm=# \d+ xx1;
                                 Table "public.xx1"
 Column |         Type          | Modifiers  | Storage  | Stats target | Description 
--------+-----------------------+------------+----------+--------------+-------------
 id     | bigint                | not null   | plain    |              | 
 name   | character varying(50) | not null   | extended |              | 
 age    | integer               | default 20 | plain    |              | 
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no

omm=# \d+ xx1;
                                 Table "public.xx1"
 Column |         Type          | Modifiers  | Storage  | Stats target | Description 
--------+-----------------------+------------+----------+--------------+-------------
 id     | bigint                | not null   | plain    |              | 
 name   | character varying(50) | not null   | extended |              | 
 age    | integer               | default 20 | plain    |              | 
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default
Has OIDs: no
Options: orientation=row, compression=no

3.查看某个模式下有哪些表

omm=# select table_name from information_schema.tables where table_schema = 'public';
-[ RECORD 1 ]----
table_name | test
-[ RECORD 2 ]----
table_name | xx1

4.查看一个表下有哪些约束

omm=# select conname, connamespace, contype, conkey     
omm-#   from pg_constraint 
omm-#  where conrelid in (  select oid
omm(#                   from pg_class
omm(#                  where relname='xx1');
omm=# -[ RECORD 1 ]+---------
conname      | xx1_pkey
connamespace | 2200
contype      | p
conkey       | {1}--或者omm=# \d xx1
 name   | character varying(50) | not null
 age    | integer               | default 20
Indexes:
    "xx1_pkey" PRIMARY KEY, btree (id) TABLESPACE pg_default

omm=#              Table "public.xx1"
 Column |         Type          | Modifiers  
--------+-----------------------+------------
 id     | bigint                | not null

5.查看一个表属于数据库的哪个模式

omm=# \x
Expanded display is on.
omm=# select * from information_schema.tables where table_name = 'xx1';
-[ RECORD 1 ]----------------+-----------
table_catalog                | omm
table_schema                 | public
table_name                   | xx1
table_type                   | BASE TABLE
self_referencing_column_name | 
reference_generation         | 
user_defined_type_catalog    | 
user_defined_type_schema     | 
user_defined_type_name       | 
is_insertable_into           | YES
is_typed                     | NO
commit_action                |